Ensure media's buffered ranges always have a range that includes currentTime.

media/filters/ffmpeg_demuxer.h

Index: media/filters/ffmpeg_demuxer.h
diff --git a/media/filters/ffmpeg_demuxer.h b/media/filters/ffmpeg_demuxer.h
index dee6db350313d830f67e5a02e5f0144952e67c2a..b181ac9f39e391addd3ba21e6c21bfde0428c4fc 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -84,6 +84,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   virtual void EnableBitstreamConverter() OVERRIDE;
   virtual const AudioDecoderConfig& audio_decoder_config() OVERRIDE;
   virtual const VideoDecoderConfig& video_decoder_config() OVERRIDE;
+  virtual Ranges<base::TimeDelta> GetBufferedRanges() OVERRIDE;
 
   // Returns elapsed time based on the already queued packets.
   // Used to determine stream duration when it's not known ahead of time.
@@ -115,6 +116,8 @@ class FFmpegDemuxerStream : public DemuxerStream {
   base::TimeDelta duration_;
   bool discontinuous_;
   bool stopped_;
+  base::TimeDelta last_packet_timestamp_;
+  Ranges<base::TimeDelta> buffered_ranges_;
 
   typedef std::deque<scoped_refptr<DecoderBuffer> > BufferQueue;
   BufferQueue buffer_queue_;
@@ -130,7 +133,7 @@ class FFmpegDemuxerStream : public DemuxerStream {
   // already been demuxed without having the demuxer thread sending the
   // buffers. |lock_| must be acquired before any access to |buffer_queue_|,
   // |read_queue_|, or |stopped_|.
-  base::Lock lock_;
+  mutable base::Lock lock_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxerStream);
 };
@@ -165,6 +168,10 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer, public FFmpegURLProtocol {
   // Provide access to FFmpegDemuxerStream.
   MessageLoop* message_loop();
 
+  // Allow FFmpegDemuxerStream to notify us when there is updated information
+  // about what buffered data is available.
+  void NotifyBufferingChanged();
+
  private:
   // To allow tests access to privates.
   friend class FFmpegDemuxerTest;